Glutamine Synthetase (GST)

  • Enzymes for Clinical Chemistry

The enzyme is useful for the determination of ammonia and ATP in clinical analysis.

Origin microorganism
Systematic name

L-Glutamate : ammonia ligase (ADP-forming)

EC Number 6.3.1.2
Reaction formula

ATP + L-Glutamate + NH3→→→ ADP + Orthophosphate + L-Glutamine

SPECIFICATION

Appearance white to light yellow lyophilizate
Activity ≧15.0 U/mg
Contaminants Catalase ≦0.5 U/U%
Stabilizer sucrose
Storage condition below-20℃

PROPERTIES

Molecular weight ca. 900 kDa (gel filtration)
Structure 57 kDa (SDS-PAGE)
Isoelectric point 6.5
Michaelis constant 1.5×10-2M (L-glutamate)
1.3×10-4M (ammonia)
8.7×10-4M (ATP)
pH Optimum ca. 7.0
pH Stability 6.5–9.5
Optimum temperature 60℃
Thermal stability below 40℃
Inhibitors methionine sulfoximine, carbamyl phosphate
Activators Mg2+,Mn2+
Specificity L-glutamate (100), D-glutamate (0.8)
NH₃(100), NH₂OH (12)
ATP (100), GTP (2.5)

APPLICATIONS

The enzyme is useful for the determination of ammonia and ATP in clinical analysis.

REFERENCES

Ebner, E. et al., “Methods in Enzymology,” Vol. 17A, Academic Press, New York, 1970, pp. 910–922.

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